Method for fabrication of lead-based perovskite materials

ABSTRACT

The disclosed invention relates to PMN compounds, powders and products thereof, especially to PMN-PT compounds, powders and products which have the perovskite structure. The PMN-PT compounds are characterized by the formula (1−x)Pb(Mg ⅓ Nb ⅔ )O 3 −xPbTiO 3  where x is about 0.0 to about 0.95, preferably x is about 0.0 to about 0.40. The compounds are made by sintering a precursor powder of the compound. PMN-PT products produced from the precursor powders have much greater densities than products produced from PMN-PT starting powder. The invention also relates to textured PMN-PT produced from the precursor powders.

[0001] This is a continuation in part of international applicationPCT/US01/06606 having an international filing date of Mar. 1, 2001.

FIELD OF THE INVENTION

[0002] The present invention relates to lead magnesium niobateperovskite compounds. More particularly, the invention relates to leadmagnesium niobate-lead titanate solid solution compounds and productsthereof. The present invention also relates to textured lead magnesiumniobate-lead titanate solid solution compounds.

BACKGROUND OF THE INVENTION

[0003] Ceramic compounds which have a perovskite crystal structure havenumerous commercial applications. These applications include: dielectricmaterials for capacitors; piezoelectric materials for transducers andsensors; electrostrictive materials for micropositioners and actuatordevices; and transparent electrooptic materials for information storageand optical signal processing.

[0004] The perovskite structure, as typified by BaTiO₃ above 135° C., iscubic. This structure is a regular array of oxygen ions at the facecenters, small tetravalent titanium ions in the center, and big,divalent barium ions located at the corners. The perovskite structure inferroelectric compounds is distorted at low temperatures and exhibitstetragonal, orthorhombic, or rhombohedral symmetry. At highertemperatures, the structure transforms to cubic. The transitiontemperature at which the distorted phase transforms to the cubic phaseis called the Curie point. The ferroelectric behavior is caused bydistortions in the crystal lattice caused by shifts in the position ofthe central cation.

[0005] A relatively new class of ferroelectric materials is PbO-basedcomplex perovskite corresponding to the formula Pb(B₁,B₂)O₃. The B₁cation can be one of several low valence cations such as Mg²⁺, Zn²⁺,Ni²⁺, and Fe³⁺, and the B₂ cation can be one of several higher valencecations such as Nb⁵⁺, Ta⁵⁺, and W⁵⁺. These ferroelectrics have promisefor dielectrics such as ceramic capacitors, piezoelectrics, andelectrostrictive actuators (e.g., micropositioner) applications,depending on composition.

[0006] Ceramic processing of ferroelectrics of lead magnesium niobate(“PMN”) by conventional milling and calcination techniques is difficult.For example, it is extremely difficult to produce PbMg_(⅓)/Nb_(⅔)O₃ byconventional mixed oxides processing due to formation of a stablePb-niobate pyrochlore phase during calcination. Repeated calcination athigh temperature (1000° C.) is required to form PMN powder. Moreover, atthese high temperatures, the volatility of PbO alters stoichiometry andprevents complete reaction. As a result, excess PbO is required.

[0007] Several processing steps are required to form a PMN powder into ashape and to densify it into a functional electrical ceramic element.The powder first is formed into a green body such as by dry pressing.The green body then is densified by sintering. Sintering is a key aspectof the manufacturing process and must be controlled to produce uniform,dense ceramic products. The uniformity and density of the productsproduced, however, are highly dependent on the ceramic powder employed.

[0008] Lead-based relaxor ferroelectric-PbTiO₃ solid solutions of theperovskite crystal structure which have the general formulaPb(B₁B₂)O₃—PbTiO₃, (“PMN-PT”)where B₁ can be any of Zn, Mg, Sc, Ni, Yb,Fe, Co, Cu, and Cd and B₂ is any of Nb, Ta, Ti, Zr, Hf, and W haveexcellent dielectric and electromechanical properties. Compounds of thisformula which are slightly on the rhombohedral side of the morphotropicphase boundary (MPB) between the tetragonal and rhombohedral phases haveexcellent dielectric and electromechanical properties. For example, thecompound 0.67PMN-0.33PT (67PMN-33PT) which is slightly on therhombohedral side of the MPB has a longitudinal piezoelectriccoefficient (d₃₃) as high as 640-700 pC/N. Also it is known that <001>oriented cuts of single crystal 65PMN-35PT have piezoelectriccoefficients (d₃₃) >1500 pC/N and longitudinal electromechanicalcoupling coefficients (k₃₃) >0.9. See Park et al., IEEE Transactions onUltrasonics, Ferroelectrics, and Frequency Control, vol. 44, pp. 1140,1997.

[0009] These properties of PMN-PT type ceramics have spawned renewedinterest in growing PMN-PT type ceramics because of their potential forimproving the performance of transducers and actuators.

[0010] Various methods have been used to grow lead-based ferroelectricsingle crystals. Typically, these methods employ the high-temperatureflux process and the Bridgeman method. These methods, however, have notbeen satisfactory. For example, the high-temperature flux process hassuffered the disadvantage of difficulty of control over thecrystallographic growth direction of the single crystals, as well ascontrol of the size of the single crystals produced. In addition, theBridgman method suffers the disadvantage of poor control over thechemical uniformity of the crystals produced. In addition to thesedisadvantages, each of these methods requires excess PbO to enhancecrystal growth. Excess PbO, however, can limit the properties attainablein the single crystals as well as cause processing difficulties. As aresult, control over the chemical uniformity of the PMN-PT crystals isexpensive and difficult.

[0011] A need therefore exists for a method of manufacture of PMN-PTtype textured ceramics which overcome these disadvantages. A need alsoexists for ceramic powders useful in manufacture of uniform, denseferroelectrics such as those based on PMN, particularly those based onsolid solutions of PMN and lead titanate (“PT”).

SUMMARY OF THE INVENTION

[0012] The present invention relates to PMN compounds, powders andproducts thereof, especially to PMN-PT compounds, powders and productswhich have the perovskite structure.

[0013] The PMN-PT compounds are characterized by the formula(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x may vary from about 0.0 to about0.95, preferably about 0.0 to about 0.40. More preferably, x is about0.35. The formula (1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ also can be expressedas (1−x)PMN−xPT where x may vary from about 0.0 to about 0.95,preferably about 0.0 to about 0.40. More preferably x is about 0.35.

[0014] In a first aspect, the invention relates to preparing leadmagnesium niobate-lead titanate compounds of the formula(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.0-0.95. The method entailsmixing a blend including a source of lead oxide with magnesium niobateand fumed titanium oxide to form a mixture. Examples of useful sourcesof lead oxide include lead acetates-lead hydroxides such asPb(CH₃COO)₂Pb(OH)₂, lead acetates such as Pb(CH₃COO)₄, leadcarbonate-hydroxides such as(PbCO₃)₂Pb(OH)₂, and lead carbonates such asPbCO₃. The mixture is milled to produce a blend of a particle size lessthan about 3 μm. Preferably, milling is performed by ball milling indistilled water. The blend is heat treated to produce a dried precursorpowder. The dried precursor powder is sintered at about 900° C. to about1300° C. to produce a lead magnesium niobate-lead titanate compound.

[0015] In a further aspect, the blend may include an oxide of any of Zr,Ta, La, Fe, Mn, Ni, Zn, and W and mixtures thereof. The blend also mayinclude a binder such as polyvinyl alcohol, polyethylene glycol,methylcellulose, carboxymethylcellulose, ethylcellulose,hydroxpropylcellulose, polyethylene oxide base high polymers, acrylicbase high polymers, maleic anhydride base high polymers, starch,gelatine, polyoxyethylene alkyl ether, polyvinyl butyrol and waxes.

[0016] In another aspect, the invention relates to a process formanufacture of 0.65PMN-0.35PT ceramics such as 0.65PMN-0.35PT singlecrystals. The process entails mixing (PbCO₃)₂Pb(OH)₂ of a particle sizeof less than about 6 μm, MgNb₂O₆ having a specific is surface area ofmore than about 5 m²/g and fumed TiO₂ having a specific surface area ofmore than about 30 m²/g to form a mixture. The(PbCO₃)₂Pb(OH)₂, fumedTiO₂₁, and MgNb₂O₆ are present in amounts sufficient to produce a ratioof (PbCO₃)₂Pb(OH)₂:MgNb₂O₆:fumed TiO₂ of about 1:0.24:0.1 to about1:0.0.27:0.12. The mixture is milled in distilled water to produce aslurry having particle size of less than about 3 μm. The slurry is heattreated to produce a dried precursor powder. The dried precursor powderis ground and sieved to a size less than about 200 μm and compressed toproduce a preform. A barium titanate single crystal template is placedon the compressed preform and an additional amount of the driedprecursor powder is placed over the barium titanate single crystal. Thepreform having the barium titanate single crystal and dried precursorpowder thereon is compressed to produce a compact. The compact issintered whereby oriented 0.65PMN-0.35PT ceramics such as 0.65PMN-0.35PTsingle crystals form on the barium titanate single crystal template.Preferably, sintering is performed at 1150° C. in 99% pure oxygen forone hour followed by sintering at 1150° C. in nitrogen for ten hours.

[0017] This aspect of the invention advantageously enables manufactureof dense PMN-PT compounds without the requirement of the prior art tocalcine dried powder and to subsequently re-mill the calcined powder.

[0018] This aspect of the invention also advantageously enablesmanufacture at low temperatures of dense products which have finemicrostructures. In addition, this aspect of the inventionadvantageously enables manufacture of PMN-PT solid solution compoundswithout the need to use excess PbO as in the prior art.

[0019] In another aspect of the invention, templated grain growth (TGG)using {001} SrTiO₃ single crystal templates are employed to producetextured, PMN_((1−x))−PT_(x) ceramics where x=0-1, preferably, about0.325 to 0.35, most preferably about 0.325, in directions such as, the<001> direction.

[0020] TGG entails growing oriented PMN-PT single crystals onto {001}SrTiO₃ single crystal templates dispersed within a PMN-PT precursormatrix. The amount of the {001} SrTiO₃ templates in the PMN-PT precursormatrix may vary from about 1 vol % to about 10 vol %, preferably about 5vol % based on the volume of PMN-PT ceramic product produced. The sizeof the {001} SrTiO₃ templates employed may vary from about 1 μm to about50 μm in edge length, preferably about 5 μm to about 25 μm in edgelength. The aspect ratio of length to thickness of the {001} SrTiO₃templates may vary from about 2 to 100, preferably about 3 to about 30,most preferably about 5 to 20.

[0021] This aspect of the invention advantageously enables use of {001}SrTiO₃ templates and a PMN-PT precursor matrix to produce texturedPMN-PT ceramics such as <001> textured PMN-PT ceramics.

[0022] The densities of the <001> textured PMN-PT ceramics produced bythis aspect of the invention advantageously are >98%, preferably >99% oftheoretical density.

[0023] Having summarized the invention, the invention will now bedescribed in detail by reference to the following detailed descriptionand non-limiting examples.

DETAILED DESCRIPTION OF THE INVENTION

[0024] In manufacture of PMN-PT compounds, a source of lead oxide ismixed with fumed TiO₂ and MgNb₂O₆ to produce a blend. Examples ofsources of lead oxide include but are not limited to lead acetates-leadhydroxides, lead acetates, lead hydroxides, and lead carbonates. Leadacetates-lead hydroxides may include Pb(CH₃COO)₂Pb(OH)₂; lead acetatesmay include Pb(CH₃COO)₄; lead hydroxides may include Pb(OH)₂.Preferably, the source of lead oxide is (PbCO₃)₂Pb(OH)₂.

[0025] The (PbCO₃)₂Pb(OH)₂ is mixed with fumed TiO₂ and MgNb₂O₆ toproduce a blend. The blend may be milled such as by jet milling or ballmilling. Preferably, the blend is ball milled in the presence of aliquid to produce a slurry of particles and liquid. More preferably,ball milling is performed for about 1 h to about 10 hours. The purity ofthe (PbCO₃)₂Pb(OH)₂ employed may vary from about 98% to about 99.99%pure, preferably about 99% to about 99.9% pure, most preferably about99.9% pure. The particle size of the (PbCO₃)₂Pb(OH)₂ can be less thanabout 6 μm, preferably less than about 5 μm, more preferably less thanabout 4 μm. The specific surface area (“SSA”) of the fumed TiO₂ can bemore than about 30 m²/g, preferably more than about 40 m²/g, morepreferably more than about 50 m²/g. The SSA of the MgNb₂O₆ can be morethan about 5 m²/g, preferably more than about 6 m²/g, more preferablyabout 7.5 m²/g. The ratios of amounts of (PbCO₃)₂Pb(OH)₂, fumed TiO₂ andMgNb₂O₆ for manufacture of 0.65PMN-0.35PT can vary. Examples of usefulratios of amounts of (PbCO₃)₂Pb(OH)₂:MgNb₂O₆:fumed TiO₂ are about1:0.24:0.1 to about 1:0.0.27:0.12, preferably about 1:0.25:0.1 to about1:0.26:0.12, more preferably about 1:0.256:0.109.

[0026] Various liquids may be used in ball milling. Examples of usefulliquids include alcohols such as ethyl alcohol, isopropyl alcohol,acetone, deionized water, and distilled water, preferably distilledwater and deionized water. Examples of milling balls which may beemployed include yittria stabilized zirconia balls and alumina balls.

[0027] The weight ratio of liquid to particles in the slurry can varyfrom about 1:0.5 to about 1:0.32. Preferably the weight ratio of liquidto particles in the slurry is about 1:0.32.

[0028] Ball milling of the mixture of (PbCO₃)₂Pb(OH)₂, fumed TiO₂ andMgNb₂O₆ is continued to produce a slurry which has a particle size lessthan about 3 μm, preferably less than about 2 μm, more preferably lessthan about 1 μm in size.

[0029] After ball milling, the slurry is heated at about 50° C. to about120° C., preferably about 60° C. to about 100° C., more preferably about70° C. to about 90° C., most preferably about 80° C., with stirring toproduce a dried PMN-PT precursor powder. The dried precursor powder isground and sieved to less than about 200 μm, preferably less than about150 μm, more preferably less than about 90 μm. The dried precursorpowder is compressed by uniaxial or isostatic pressure to produce acompact. The compact then is isostatically compressed to produce a greenpreform. Uniaxial pressing may be done at about 5 MPa to about 100 MPa,preferably about 5 MPa to about 50 MPa, more preferably about 5 MPa toabout 20 MPa. Isostatic pressing may be done at about 100 MPa to about400 MPa, preferably about 100 MPa to about 350 MPa, more preferablyabout 100 MPa to about 300 Mpa.

[0030] The green preform then is sintered. During sintering, the greenpreform is encapsulated in Nobel metal foil such as Pt and placed intoan embedding powder. Embedding powders which may be used include leadcontaining powders such as lead oxide, lead magnesium niobate, and leadzirconium niobate. These powders are capable of surrounding the preformwith an atmosphere of lead oxide during sintering. In manufacture ofPMN-PT compounds, the embedding powder preferably has about 1% more PbOthan the PMN-PT composition of the green preform. More preferably, thepowder has the same composition as the green preform.

[0031] The embedding powder preferably has a composition identical tothe green preform to provide an atmosphere of lead oxide around thegreen preform. Where the embedding powder has a composition identical tothat of the green preform, encapsulation of the green preform in thenoble metal foil is optional.

[0032] The green preform can be sintered in oxygen, nitrogen, or air. Ina preferred aspect, the preform is sintered in oxygen, preferably 95%pure oxygen, more preferably 99% pure oxygen. In another preferredaspect, the preform is sintered in oxygen and then in nitrogen. Duringsintering, the green preform may be heated at about 3° C. to about 20°C./min, preferably about 5° C. to about 15° C./min, more preferablyabout 10° C. to about 15° C./min, most preferably about 15° C./min.

[0033] Sintering temperatures can vary from about 900° C. to about 1300°C., preferably about 1000° C. to about 1200° C., more preferably about1000° C. to 1150° C. The time periods at which the preform is held atthe sintering temperature can be up to about 50 hours, preferably about0.5 to about 20 hours, more preferably about 1 to about 10 hours.

EXAMPLES 1-3 Manufacture of 0.65PMN-0.35PT That Has the PerovskiteCrystal Structure Example 1

[0034] 51.6 g (PbCO₃)₂Pb(OH)₂ of 99.9% purity from Aldrich Chemical Co.that has an average particle size of 3.7 μm is blended with 13.2 gMgNb₂O₆ of 99.9% purity from H. C. Starck Co. which has a specificsurface area of 7.43 m²/g and with 5.6 g fumed TiO₂ from Degussa Corp.that has a specific surface area of 50 m²/g to produce a blend. Theblend is ball milled for 10 h with 700 gm of 3 mm diameter yittriastabilized ZrO₂ balls from Tosoh Corp. Ball milling is done in 220 mldeionized water in a 500 ml, high density polyethylene bottle to producea slurry.

[0035] After ball milling, the slurry is placed in a glass beaker andheated on a hot plate at 80° C. for 12 hours in air while stirring witha magnetic stirrer. The resulting material then is dried at 80° C. in anoven for 5 hours in air to produce a dried precursor powder of0.65PMN-0.35PT. The precursor powder is considered dry when the absorbedwater content remaining in the powder is less than about 0.3% by weightof the powder, or when chemically bound water is less than about 1.7% byweight of the powder. The dried precursor powder is ground and sieved toa particle size of −170 mesh, that is, less than 90 μm.

[0036] The dried precursor powder in an amount of 0.3 g is placed into aquarter inch diameter die and uniaxially compressed at 5 MPa to producea compact. The compact is isostatically pressed at 280 MPa to produce agreen preform that has a density of 4.13 g/cc.

[0037] The green preform is encapsulated in platinum foil. Theencapsulated green preform is placed in an embedding powder of the samecomposition as the green preform in an alumina boat. The green preformis sintered in 99% pure oxygen in a tube furnace. During sintering, thepreform is heated at 15° C./min to a temperature of 1000° C. The preformis held at 1000° C. for one hour to produce a sintered product of0.65PMN-0.35PT.

Example 2

[0038] The procedure of example 1 is repeated except that the preform isheld at 1000° C. for 4 hours.

Example 3

[0039] The procedure of example 1 is repeated except that the preform isheld at 1000° C. for 11 hours.

[0040] The densities of the sintered products produced in examples 1-3are shown in column 3 of Table 1.

Comparison Examples 1C-3C

[0041] For comparison, the procedure of example 1 is repeated exceptthat commercially available 0.65PMN-0.35PT powder of a particle size of1.33 μm from TRS Corp. is compressed to make the green preform which issintered. The densities of the sintered products produced from thecommercially available 0.65PMN-0.35PT powder are shown in column 4 ofTable 1. TABLE 1 Sintered Densities Sintered Sintered Density of Densityfrom 0.65 PMN-0.35 PT Commercial Sintering Time from Powder of 0.65PMN-0.35 PT in 99% Pure Invention Perovskite Example Oxygen (hours)(g/cc) Powder (g/cc) 1  1 8.075 — 2  4 8.126 — 3 11 8.136 — 1C  1 —7.902 2C  4 — 8.009 3C 11 — 7.972

[0042] The results in Table 1 show that the dried precursor powders asin of the invention sinter to produce PMN-PT ceramic products which havegreater densities than the products produced from commercial PMN-PTpowders such as commercial perovskite 0.65PMN-0.35PT powder. In additionto greater densities, the microstructure of the sintered productsproduced from the dried PMN-PT precursor powders is more dense and morefine than that produced from sintering of commercial PMN-PT perovskitepowder.

EXAMPLES 4-13 These Examples Illustrate the Effect of Temperature, Timeand Atmosphere on Sintered Density Example 4

[0043] The procedure of example 1 is followed except that the greenpreform is heated to a sintering temperature of 1150° C. in 99% pureoxygen, and then immediately cooled.

Example 5

[0044] The procedure of example 4 is followed except that the preform ismaintained at a sintering temperature of 1150° C. in oxygen for 0.5hours prior to cooling.

Example 6

[0045] The procedure of example 4 is followed except that the preform ismaintained at a sintering temperature of 1150° C. in air for 0.5 hourprior to cooling.

Example 7

[0046] The procedure of example 4 is followed except that the preform ismaintained at a sintering temperature of 1150° C. in 99% pure oxygen for1 hour prior to cooling.

Example 8

[0047] The procedure of example 4 is followed except that the preform ismaintained at a sintering temperature of 1150° C. in 99% pure oxygen for1 hour prior to changing the atmosphere to nitrogen. The preform issintered at 1150° C. in nitrogen for 1 hour prior to cooling.

Example 9

[0048] The procedure of example 4 is followed except that the preform ismaintained at a sintering temperature of 1150° C. in 99% pure oxygen for1 hour prior to changing the atmosphere to nitrogen. The preform issintered at 1150° C. in nitrogen for 3 hours prior to cooling.

Example 10

[0049] The procedure of example 4 is followed except that the preform ismaintained at a sintering temperature of 1150° C. in 99% pure oxygen for4 hours prior to cooling.

Example 11

[0050] The procedure of example 4 is followed except that the preform ismaintained at a sintering temperature of 1150° C. in air for 6 hoursprior to cooling.

Example 12

[0051] The procedure of example 4 is followed except that the preform ismaintained at a sintering temperature of 1150° C. in 99% pure oxygen for1 hour prior to changing the atmosphere to nitrogen. The preform issintered at 1150° C. in nitrogen for 10 hours prior to cooling.

Example 13

[0052] The procedure of example 4 is followed except that the preform ismaintained at a sintering temperature of 1150° C. in 99% pure oxygen for11 hours prior to cooling.

[0053] The densities of the sintered products produced as in examples4-13 are measured by the Archimedes method. The results are shown inTable 2. TABLE 2 Effect of Sintering Atmosphere on Sintered DensityDensity Produced Density Total by Sintering Produced by DensitySintering in Oxygen Sintering in Produced by Ex- Time (Hours) followedby 99% Pure Sintering in ample at 1150° C. Nitrogen (g/cc) Oxygen (g/cc)Air (g/cc)  4  0 — 7.840 —  5  0.5 — 8.082 —  6  0.5 — — 7.962  7  1 —8.116 —  8  2 8.093 — —  9  4 8.100 — — 10  4 — 8.080 — 11  6 — — 7.90012 11 8.140 — — 13 11 — 8.094 —

[0054] The microstructures of the sintered products of examples 4, 5,7-10, 12 and 13 are free of pores at the grain boundaries. In contrast,the products of examples 6 and 11 have pores at the grain boundaries.

EXAMPLE 15 Manufacture of 0.70PMN-0.30PT That Has the Perovskite CrystalStructure

[0055] The procedure of example 1 is repeated except that the amount of(PbCO₃)₂Pb(OH)₂ is 48.259 g, the amount of MgNb₂O₆ is 13.2 g and theamount of fumed TiO₂ is 4.43 g.

EXAMPLE 16 Manufacture of 0.68MN-0.32PT That Has the Perovskite CrystalStructure

[0056] The procedure of example 1 is repeated except that the amount of(PbCO₃)₂Pb(OH)₂ is 48.774 g, the amount of MgNb₂O₆ is 12.993 g and theamount of fumed TiO₂ is 4.899 g.

EXAMPLE 17 This Example Illustrates Manufacture of Single Crystal0.65PMN-0.35PT.

[0057] Barium titanate single crystals grown by the Remeika salt processare used for the seed particle to grow 0.65PMN-0.35PT single crystal. Inthe Remeika salt process, the barium titanate single crystal is made bymixing 18.3 g of KF from Acros Chemical with 8.79 g BaTiO₃ from CabotPerformance Materials in a 40-ml platinum crucible. The resultingmixture is heated at 10° C./min to a 1100° C. in air. The mixture isheld at 1100° C. for 240 minutes, cooled to 850° C. over a period of 720min, and then quenched in air at room temperature. Residual KF isremoved by washing with deionized water. The resulting barium titanatesingle crystal then is cut to measure 2 mm×2 mm×0.1 mm.

[0058] 0.15 g of the dried precursor powder prepared as in example 1 isfilled into a quarter inch diameter die and uniaxially compressed at 0.5MPa to form a green pellet. The 2 mm×2 mm×0.1 mm size BaTiO₃ singlecrystal produced above is placed on the green pellet while in the die.An additional 0.15 g of the same dried precursor powder is poured intothe die over the BaTiO₃ single crystal. The pellet with powder andBaTiO₃ single crystal is uniaxially compressed at 5 MPa to produce acompact. The compact then is isostatically compressed at 280 MPa toyield a green preform. The green preform is sintered as in example 4. A0.65PMN-0.35PT single crystal is formed on the BaTiO₃ crystal. The sizeof the 0.65PMN-0.35PT single crystal is measured by scanning electronmicroscopy.

EXAMPLE 17C

[0059] For comparison, the procedure of example 17 is followed exceptthat commercial 0.65PMN-0.35PT perovskite powder from TRS of example 1Cis substituted for the dried precursor powder employed in example 17.

[0060] Comparison of the sizes of the 0.65PMN-0.35PT single crystalgrown with the 0.65PMN-0.35PT with the precursor material of theinvention with the single crystal grown with the commercial0.65PMN-0.35PT perovskite material shows that the single crystal grownwith the precursor material of the invention is significantly larger.The 0.65PMN-0.35PT single crystal grown by use of the precursor powderof the invention is an order of magnitude greater than the0.65PMN-0.35PT single crystal produced from the commercial0.65PMN-0.35PT perovskite powder.

[0061] As an alternative to use of BaTiO₃ single crystal templates,PbTiO₃ single crystal templates may be used. PbTiO₃ single crystaltemplates can be grown by the following procedure:

[0062] An aqueous 0.5 M stock Pb-acetate (Pb(CH₃COO)₂) (Aldrich ChemicalCo.) solution was made in de-ionized water. A stock 0.5 MTi-isopropoxide (Ti(OPr^(i))₄) (Aldrich Chemical Co.) solution inethanol was prepared and stored in an argon filled glove-box. KOH wasthen added to de-ionized water to form a 2 M stock KOH solution. 0.1 wt% polyvinyl alcohol (PVA) was added to the KOH stock solution.

[0063] The Ti-isopropoxide solution was added to the Pb-acetate solutionin a 21 ml. Teflon-lined Parr hydrothermal autoclave (Parr InstrumentCompany, Moline, Ill.) at a Pb/Ti ratio=1.4. The 2 M KOH solution wasadded to the Parr autoclave until the pH was 13.8. The addition of theKOH produced a thick yellowish-white gel in the Parr autoclave. The gelfilled 50 vol % of the Teflon autoclave cell. The Parr autoclave wassealed and heated to 165° C. for 5 h. The resultant powdered cake wasfilter-washed with de-ionized water. The pH of the wash water wasaltered to −10 by NH₄OH to decrease Pb leaching from the PbTiO₃particles during washing. The PbTiO₃ fibers are <1 μm in diameter andbetween 10-20 μm in length. The acicular particles crystal structurechanged to the tetragonal PbTiO₃ structure above 650° C. withoutaltering the morphology of the particles.

EXAMPLE 18-19 These examples shows the effect of Sintering Atmosphere on0.65PMN-0.35PT Single Crystal on BaTiO₃ Single Crystal Template Example18

[0064] A green preform is prepared as in Example 17. The preform issintered at 1150° C. for 1 hour in oxygen followed by sintering at 1150°C. for 10 hours in nitrogen.

[0065] The 0.65PMN-0.35PT single crystal ceramics produced have aperovskite crystal structure and a density of about 99.0% theoretical asdetermined by X-ray diffraction and scanning electron microscopy.

Example 19

[0066] A green preform is prepared as in Example 17. The preform issintered in air at 1150° C. for 11 hours.

[0067] Comparison of examples 18 and 19 shows that the 0.65PMN-0.35PTsingle crystal of example 18 is very dense and is free of entrappedpores. In contrast, entrapped pores are observed in the 0.65PMN-0.35PTsingle crystal of example 19.

[0068] The invention also may be used to manufacture PMN ferroelectriccompounds per se as described below in example 20.

EXAMPLE 20

[0069] The procedure of example 1 is repeated except that only(PbCO₃)₂Pb(OH)₂ and MgNb₂O₆ is employed. The amount of (PbCO₃)₂Pb(OH)₂is 48.1 g and the amount of MgNb₂O₆is 18.983 g. The ratio of(PbCO₃)₂Pb(OH)₂ to MgNb₂O₆ is 1:0.395.

EXAMPLE 21

[0070] The procedure of example 17 is repeated except that PbTiO₃ singlecrystals are substituted for BaTiO₃ single crystals.

[0071] In another aspect of the invention, textured PMN-PT ceramics areproduced. In this aspect, anisotropic, {001} SrTiO₃ single crystaltemplates are employed in manufacture of textured PMN-PT ceramics. Inthis aspect of the invention, anisotropic, {001} SrTiO₃ single crystaltemplates are mixed with a PMN-PT precursor matrix material, an organicliquid, binder and optional modifier to form a slurry. The slurry thenis dried to form a powder which is sintered to form textured PMN-PTceramics on the {001} SrTiO₃ single crystal templates.

[0072] The anisotropic {001} SrTiO₃ single crystal templates employedare produced as taught in Applicants copending application U.S. Ser. No.09/558,049, the teachings of which are incorporated by reference intheir entirety herein. As taught in application Ser. No. U.S.09/558,049, the anisotropic {001} SrTiO₃ single crystal templatesemployed have rectangular faces which measure about 10 μm to about 40 μmin edge length, and about 2 μm to about 5 μm in thickness. The aspectratio of length to thickness of the {001} SrTiO₃ single crystaltemplates may vary from about 1 to about 20.

[0073] As taught in Applicants copending application U.S. Ser. No.09/558,049, the micron size anisotropically shaped SrTiO₃ single crystaltemplates are obtained by molten salt synthesis of tabular Sr₃Ti₂O₇particles, followed by reaction of the tabular Sr₃Ti₂O₇ particles andTiO₂ in molten KCl. During this reaction, anisotropically shaped singlecrystal SrTiO₃ forms on the surface of the tabular Sr₂Ti₃O₇. The singlecrystal SrTiO₃ particles form in an epitaxial relationship with thetabular Sr₃Ti₂O₇ wherein the [001] of SrTiO₃ is parallel to the [001] ofSr₂Ti₃O₇. Reaction of the tabular Sr₃Ti₂O₇ particles and TiO₂ in moltenKCl is driven to completion to yield unsupported, anisotropically shapedSrTiO₃ particles.

[0074] In manufacture of the anisotropic, {001} SrTiO₃ single crystaltemplates, the SrCO₃, TiO₂, Sr₃Ti₂O₇, and salts such as KCl which areemployed are about 99.9% pure. Generally, however, these reactants orprecursors thereof can be of commercial or a technical grade.

[0075] The reactants or precursors thereof which are employed inmanufacture of the anisotropic single crystal SrTiO₃ templates typicallyhave a particle size range from submicron up to about 100 μm. Thereactants or precursors thereof preferably are free of large, hardaggregates of about 100 μm or more in size.

[0076] The tabular Sr₃Ti₂O₇ particles employed in manufacture of theSrTiO₃ single crystal templates typically measure about 100 μm in lengthand about 10 μm in thickness, preferably about 10 μm to about 40 μm inlength and about 2 μm to about 5 μm in thickness, and the aspect ratioof length to thickness of the tabular Sr₃Ti₂O₇ particles may range fromabout 1 to about 20, preferably about 10.

[0077] In order to prepare the tabular Sr₃Ti₂O₇ particles, SrCO₃ andTiO₂ powders, each of which have a particle size of about 10 μm to about0.1 μm, preferably about 0.1 μm, are mixed by ball milling with plasticball media in a polar solvent such as ethanol, isopropanol, acetone, andmethanol to produce a slurry. The SrCO₃ and TiO₂ may be used in molarratios of SrCO₃::TiO₂ of from about 3.0:2.0 to about 3.3:2.0, preferablyabout 3.2:2.0. Mixing is continued for a time sufficient to achieve ahomogenous slurry, typically about 8 hours. After completion of mixing,a salt is added to the slurry and ball milled, typically about 3 hours.The salt which is added is water soluble, has solubility for SrO andTiO₂, does not become incorporated into the crystals of the productphase, and has low volatility. The amount of salt added to the slurry isabout 50% to about 150%, preferably about 100% of the combined weight ofthe SrCO₃ and TiO₂ reactants. Examples of salts which may be employedinclude KCl, NaCl, and mixtures thereof, preferably KCl.

[0078] The above formed slurry of SrCO₃, TiO₂ and salt is dried in airbetween about 25° C. to about 90° C., preferably about 85° C. Theresulting dried powder is placed in a crucible such as alumina orplatinum, preferably alumina. Preferably, an alumina lid is placed ontop of the alumina crucible, and the edges of the lid are sealed withalumina cement to prevent evaporation of the salt. The powder in thesealed crucible is fired at about 1200° C. to about 1400° C., preferably1300° C., for about 1 hour to about 8 hours, preferably about 4 hours.During firing, the heating rate is about 2° C./min to about 40° C./min.,preferably 10° C./min. After completion of firing, the powder in thesealed crucible is cooled to room temperature at the rate of about 1°C./min to about 100° C./min., preferably about 3° C./min to about 5°C./min. The resulting tabular Sr₃Ti₂O₇ particles are washed withdeionized water at a temperature of about 25° C. to about 99° C.,preferably about 90° C., to remove about 98% or more of the salt,preferably about 99.9% or more of the salt.

[0079] The tabular Sr₃Ti₂O₇ particles produced as described above may beemployed in a wide range of sizes and aspect ratios for reaction withTiO₂ to produce anisotropically shaped, single crystal SrTiO₃ templates.Any polymorph of TiO₂ may be used, preferably, fumed TiO₂.

[0080] The tabular Sr₃Ti₂O₇ particles are combined with TiO₂, preferablyin a polar solvent such as ethanol to produce a slurry. The amounts ofSr₃Ti₂O₇ and TiO₂ are sufficient to yield a molar ratio of Sr₃Ti₂O₇ toTiO₂ of about 1:1 to about 1:1.3, preferably about 1.0:1.1. The slurryis mixed by a magnetic stirrer for about 0.5 hour to about 10 hours,preferably about 1 hour. After completion of mixing, a water-solublesalt that has solubility for SrO and TiO₂ has low volatility, and doesnot become incorporated into the crystals of the product phase is mixedwith the Sr₃Ti₂O₇ and TiO₂. Preferably, the salt is added to a slurry ofSr₃Ti₂O₇ and TiO₂. Examples of useful salts include KCl, NaCl ormixtures thereof, preferably KCl. The amount of salt added is about 50%to about 150%, preferably about 100%, of the combined weight of Sr₃Ti₂O₇and TiO₂.

[0081] The resulting slurry of Sr₃Ti₂O₇, TiO₂ and salt is dried at about25° C. to about 75° C., preferably about 65° C., for about 1 hour toabout 10 hours, preferably about 5 hours. The resulting dried powder isfired at a heating rate of about 1° C./min to about 40° C./min,preferably about 10° C./min, in an alumina crucible, preferably acovered alumina crucible, to about 700° C. to about 1400° C., preferablyabout 1200° C., for about 60 to about 480 minutes, preferably about 240min.

[0082] After completion of firing, the resulting fired powder in thecrucible is cooled to room temperature at about 1° C./min to about 40°C./min., preferably about 5° C./min. The salt is removed from the firedpowder by washing with deionized water at a temperature of about 25° C.to about 90° C., preferably about 90° C., to remove about 98% or more ofthe KCl, preferably about 99.9% or more of the KCl.

[0083] The anisotropically shaped, single crystal SrTiO₃ forms on thesurface of the tabular Sr₃Ti₂O₇ particles by epitaxial growth. To enableepitaxial growth, the lattice mismatch between the Sr₃Ti₂O₇ substrateand the growing SrTiO₃ typically is less than about 15%. Preferably, thedifference in lattice parameters between the SrTiO₃ and the substrate isas small as possible.

[0084] In this aspect of the invention, the reactant materials used tomake the PMN-PT precursor matrix material include (Pb(CO₃))₂Pb(OH)₂ fromAldrich Chemical Co., fumed TiO₂ from DeGussa, and MgNb₂O₆ from H. C.Starck. Preferably, fumed TiO₂ is used. However, any polymorph of TiO₂may be used. These reactants typically have about 99.9% purity.Generally, however, these reactants may have a purity of a technicalgrade.

[0085] The Pb(CO₃)₂Pb(OH)₂ may be employed in particle sizes less thanabout 6 μm, preferably less than about 5 μm, most preferably less thanabout 4 μm. The fumed TiO₂ employed typically has a specific surfacearea (“SSA”) of more than about 30 m²/g, preferably more than about 40m²/g, more preferably more than about 50 m²/g. The particle sizes of theMgNb₂O₆ employed may have a SSA greater than about 5 m²/g, preferablygreater than about 6 m²/g, more preferably greater than about 7.5 m²/g.The (PbCO₃)₂Pb(OH)₂, the fumed TiO₂, and the MgNb₂O₆ employed in thisaspect of the invention may be used in amounts sufficient to produce aratio of (PbCO₃)₂Pb(OH)₂:MgNb₂O₆:fumed TiO₂ of about 1:0.24:0.1 to about1:0.0.27:0.12.

[0086] The PMN-PT precursor matrix material employed can be a reactivePMN-PT precursor matrix material, a calcined PMN-PT precursor matrixmaterial, or mixtures thereof. The particle size of the PMN-PT precursormatrix material may vary from about 0.2 μm to about 2 μm, preferablyabout 0.2 μm.

[0087] In manufacture of the PMN-PT matrix precursor matrix material,(Pb(CO₃))₂Pb(OH)₂, fumed TiO₂, and MgNb₂O₆ are ball milled with plasticball media in deionized water to produce a milled slurry. In a firstembodiment for manufacture of the PMN-PT matrix precursor matrixmaterial, the milled slurry is dried, ground to about 50 μm to about 150μm, preferably about 90 μm to yield a reactive PMN-PT precursor matrixmaterial that is mixed with the SrTiO₃ templates. In a second embodimentfor manufacture of the PMN-PT matrix precursor matrix material, thereactive PMN-PT precursor matrix material produced as in the firstembodiment is calcined prior to addition of the SrTiO₃ templates. ThePMN-PT precursor matrix material can be calcined at about 550° C. toabout 800° C. for abbout 5 minutes to about 20 hours, preferably about 5minutes to about 10 hours, more preferably about 700° C. for about 1hour. In a third embodiment for manufacture of the PMN-PT matrixprecursor matrix material, excess PbO in an amount of up to about 8%beyond that required to produce stoichiometric PMN-PT is added to theprecursor mixture of (Pb(CO₃))₂Pb(OH)₂, fumed TiO₂, and MgNb₂O₆ prior toaddition of SrTiO₃ templates.

[0088] The PMN-PT precursor matrix material is mixed with {001} SrTiO₃templates and an organic liquid such as any of toluene, ethyl alcohol,acetone and water, preferably, a binder such as any of polyvinyl butyraland polyvinyl alcohol, preferably a polyvinyl butyral binder such asFerro 73210 from the Ferro Corp., and an optional modifier such as Ferro1111 to form a slurry. The binder may be employed in an amount of about50 wt. % to about 70 wt % based on the weight of the PMN-PT precursormatrix material. The modifier may be used in an amount of about 0.5 wt %to about 1.5 wt %, based on the weight of the PMN-PT precursor matrixmaterial.

[0089] The amount of organic liquid added to the PMN-PT precursor matrixmaterial may be about 70 wt % to about 100 wt % based on the weight ofthe PMN-PT precursor matrix material.

[0090] The amount of {001} SrTiO₃ single crystal templates employed withthe PMN-PT precursor matrix material may vary from about 1 vol % toabout 10 vol %, preferably about 5 vol % based on the volume of thePMN-PT product produced. The size of the {001} SrTiO₃ templates employedwith the PMN-PT precursor matrix material may vary from about 1 μm toabout 50 μm in edge length, preferably about 5 μm to about 25 μm in edgelength, and about 1 μm to about 10 μm in thickness, preferably about 2μm to about 5 μm thickness. The aspect ratio of length to thickness ofthe {001} SrTiO₃ single crystal templates may vary from about 1 to about20, preferably about 10.

[0091] The slurry of PMN-PT precursor matrix material and {001} SrTiO₃single crystal templates is formed into shapes suitable for stackinginto an assembly which can be compressed into a laminate. The shapes maybe formed by methods such as tape casting, extrusion, roll compaction,injection molding and uniaxial pressing, preferably tape casting. Theshapes used to form the assembly typically have a configuration in theform of a square.

[0092] When the shapes are formed by tape casting, excess organic liquidis evaporated to yield a slurry of a viscosity of about 100 mPa•s toabout 1000 mPa•s, preferably about 150 mPa•s. Tape casting typically isperformed by casting the slurry at a shear rate of about 150 s⁻¹ toabout 500 s⁻¹, preferably about 360 s⁻¹ onto a glass substrate. Tapecasting is performed with an aluminum doctor blade machine from the R.J. Carston Co. The gap used in the machine typically is about 150 μm toabout 500 μm, preferably about 150 μm to about 300 μm, more preferablyabout 200 μm.

[0093] When tape casting, the thickness of the cast tape formedtypically is about 30 μm to about 200 μm, preferably about 50 μm. Thecast tape is dried at about 25° C. for about 10 hours to removevolatiles. The resulting dried tape then is cut into shapes such assquares, stacked into an assembly of 5 to 50 layers, preferably 50layers, and uniaxially compressed under a pressure of about 2,000 PSI toabout 20,000 PSI, preferably about 4,000 PSI to produce a laminate. Thelaminate then is heated to burnout the binder prior to sintering toyield a green preform.

[0094] The binder and organics can be removed by first heating thesample at 0.5° C./min to 200° C., holding at 200° C. for 1 h, heating at0.35° C./min to 275° C., holding at 275 OC. for 1 h, heating at 0.5°C./min to 600° C., holding at 600° C. for 1 h, and then cooling to roomtemperature at 2° C./min in air.

[0095] The green preform, during sintering, is heated at about 1° C./minto about 15° C./min, preferably at about 15° C./min to a sinteringtemperature of about 900° C. to about 1250° C., preferably about 1150°C. and held at the sintering temperature in flowing oxygen for about 1 hto about 50 h, preferably about 10 h. The resulting product is texturedPMN-PT ceramic.

[0096] The following non-limiting examples 21-23 illustrate manufactureof textured PMN-PT ceramics with use of SrTiO₃ single crystal templates.

EXAMPLES 21-22 These Examples Illustrate Manufacture of Textured0.675Pb(Mg_(⅓)Nb_(⅔))O₃−0.325 PbTiO₃ (67.5 PMN-32.5PT) Ceramics UsingSrTiO₃ Single Crystal Templates and 67.5PMN-32.5PT Reactive PrecursorMatrix Material Example 21

[0097] A. Manufacture of 67.5PMN-32.5PT Reactive Precursor matrixmaterial

[0098] 48.774 gms (Pb(CO₃))₂Pb(OH)₂ of particle size less than 4 micron,4.899 gms fumed TiO₂ of specific surface area of more than 50 m²/gm, and12.993 gms MgNb₂O₆ of a specific surface area of more than about 7.5m²/gm are mixed in a ball mill with plastic media in deionized water toproduce a milled slurry. The milled slurry is dried at 80° C. for 10hours, ground in mortar and pestle, and sieved to <90 μm (−170 mesh) toyield a reactive 67.5PMN-32.5PT precursor matrix material.

[0099] B. Manufacture of textured 67.5 PMN-32.5PT textured ceramics

[0100] 15 g of the 67.5PMN-32.5PT precursor powder produced above isadded to 12 g toluene, 8.25 g Ferro 73210 binder and 0.188 g Ferro 1111modifier, and milled for 24 h using ZrO₂ milling media to obtain amilled slurry of a particle size of 1 μm. After milling, 0.5 g of theSrTiO₃ templates produced as above and which is dispersed in 10 gmtoluene are added to the 67.5PMN-32.5PT precursor powder. Excess tolueneis removed by evaporation while stirring with a stir bar in a beakeruntil the slurry reaches a viscosity of 150 mPa•s. The slurry is tapecast at a blade gap of 200 μm at a shear rate of 360 s⁻¹. The resultingtape is cut into squares, stacked into an assembly of 30 layers, andcompressed under a pressure of 19000 PSI to yield a 1 mm thick laminatedsample. The sample is heated to burn out the binder and organics toproduce a green preform. The preform then is sintered.

[0101] During binder burn out to remove organics, the sample is heatedat 0.5° C./min to 200° C., held at 200° C. for 1 h, heated at 0.35°C./min to 275° C., held at 275° C. for 1 h, and then heated at 0.5°C./min to 600° C. and then held at 600° C. for 1 h. The sample then iscooled to room temperature at 2° C./min in air to produce a greenpreform.

[0102] During sintering, the green preform is encapsulated in platinumfoil and then embedded in the above formed 67.5PMN-32PT precursor matrixpowder in an alumina boat. The green preform then is heated at 15°C./min to 1150° C. and held at 1150° C. for 10 h in flowing, 99% pureoxygen. The preform than is cooled at 15° C./min. to room temperature toproduce textured 67.5PMN-32.5PT ceramics.

Example 22

[0103] The procedure of example 21 is followed except that the sample isheld at the sintering temperature of 1150° C. for 50 h.

[0104] The degrees of texture of the 67.5PMN-32.5PT ceramics produced inexamples 21 and 22 is estimated by comparing X-ray peak intensities oftextured and untextured 67.5PMN-32.5PT samples. The samples are groundusing 800 mesh and 2400 mesh SiC paper prior to measurement of X-raypeak intensities and piezoelectric properties such as polarization andstrain hysteresis.

[0105] Polarization and strain hysteresis measurements are performed byusing a modified Sawyer-Tower circuit and a linear variable displacementtransducer (LVDT) driven by a lock in amplifier (Stanford ResearchSystems model SR 830). Electric fields as high as 50 kV/cm are employedfor strain measurements using an amplified unipolar wave at 0.1 Hz froma TREK 609C-6 high voltage D.C. amplifier. The samples were immersed inGALDEN, HT-200 insulating liquid from Galden Co. during thesemeasurements. Samples were poled prior to strain measurements and theconditions for poling were optimized as is well known in the art. Anamplified triangular waveform is used to measure polarizationhysteresis.

[0106] Table 3 below compares the X-ray patterns of textured67.5PMN-32.5PT produced as in Example 21 with random untextured67.5PMN-32.5PT. As shown in Table 3, the textured 67.5PMN-32.5 PT ofexample 21 has highly developed (001) and (002) peaks and a suppressed(110) peak, which is the main peak for the random untextured67.5PMN-32.5PT ceramic. This confirms formation of textured67.5PMN-32.5PT. TABLE 3 Comparison of relative peak intensities (%) oftextured and untextured 67.5 PMN-32.5 PT Example 21: Textured Untextured67.5 PMN-32.5 PT 67.5 PMN-32.5 PT Sintered for 10 hrs at Sintered for 50hrs at Plane 1150 C. 1150 C. (100) 21 100  (110) 100  28 (111) 34 (200)27 91 (210) 10  7 (211) 33

[0107] The microstructures of the textured 67.5PMN-32.5PT ceramicsproduced by sintering for 10 h and 50 h at 1150° C. as above shows thataligned, blocky grains are dispersed in a fine grain matrix. Thesemicrostructures also show the improved grain alignment that produced.

[0108] Table 4 shows the piezoelectric strain of textured 67.5PMN-32.5PTof example 21 produced by sintering for 50 h at 1150° C. TABLE 4Piezoelectric strain of the textured 67.5 PMN-32.5 PT of Example 21produced by sintering for 50 h at 1150° C. Strain at Strain at 50 d₃₃ upto 10 10 kV/cm kV/cm kV/cm Example 21: 0.16% 0.31% 1200 pC/N Textured67.5 PMN-32.5 PT Untextured 0.09% 0.15%  580 pC/N 67.5 PMN-32.5 PT

[0109] The textured 67.5PMN-32.5PT of example 21-please confirm of 0.7mm thickness is translucent. This confirms absence of porosity andabsence of impurities at the grain boundaries.

EXAMPLE 22 This Example Illustrates Use of Calcined PMN-PT PrecursorMatrix Material and SrTiO₃ Single Crystal Templates in Manufacture ofTextured PMN-PT Ceramics

[0110] 11.08 g of the 67.5PMN-32PT precursor matrix material prepared asin example 20 is calcined at 700° C. for 1 h. The resulting calcinedprecursor matrix material is added to 9 g toluene 6 g binder (Ferro73210), 0.15 g modifier (Ferro 1111) and milled for 24 h using ZrO₂milling media to yield a milled slurry. After milling, 0.41 g of SrTiO₃templates prepared as above and dispersed in toluene, are added to theslurry. Samples were prepared and sintered following the procedure ofExample 20.

[0111] Table 5 compares the texture development of 67.5PMN-32.5PTceramic, as gauged by the Lotgering Factor, produced by use of reactiveand calcined precursor matrix materials by sintering at 1150° C. Thecalcined 67.5PMN-32.5PT precursor matrix retains good reactivity whencalcined at low temperature to prevent particle coarsening. TABLE 5Lotgering Factor of Textured 67.5 PMN-32.5 PT Produced after sinteringat 1150° C. from Reactive and calcined 67.5 PMN-32.5 PT precursor matrixmaterials Calcined 67.5 PMN- Sintering Reactive 67.5 PMN-32.5 PT 32.5 PTprecursor time (h) precursor matrix matrix 0 0.21 0.19 1 0.53 0.54 20.52 0.59 4 0.54 0.60 10  0.59 0.65 50  0.62 0.70

EXAMPLE 23 This Example Illustrates Manufacture of 67.5PMN-32.5 PTTextured Ceramics by Use of Excess PbO in 67.5PMN-32.5PT PrecursorMatrix Material

[0112] A mixture of reactive 67.5PMN-32.5 PT prepared as in example 20is mixed with 3% excess PbO beyond that required to form astoichiometric 67.5PMN-32.5PT.

[0113] The forgoing has been described in connection with manufacture ofPMN-PT compounds, particles and sintered products thereof. It should berecognized, however, that the invention is applicable to manufacture ofa wide range of compounds. For example, the invention may be used tomanufacture compounds of solid solutions of PMN-PT which include cationsof elements such as Zr, Ta, La, Fe, Mn, Ni, Zn, and W.

What is claimed is:
 1. A process for preparing(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.35 comprising, mixing(PbCO₃)₂Pb(OH)₂ of a particle size less than about 6 μm, MgNb₂O₆ havinga specific surface area of more than about 5 m²/g and fumed TiO₂ havinga specific surface area of more than about 30 m²/g to form a mixture,the (PbCO₃)₂Pb(OH)₂, the fumed TiO₂, and the MgNb₂O₆ present in amountssufficient to produce a ratio of (PbCO₃)₂Pb(OH)₂:MgNb₂O₆:fumed TiO₂ ofabout 1:0.24:0.1 to about 1:0.0.27:0.12, milling the mixture indistilled water to produce a slurry having particle size of less thanabout 3 μm, heat treating the slurry to produce a dried precursorpowder, grinding the dried precursor powder to a size less than about200 μm, and sintering the dried precursor powder to a temperature ofabout 900° C. to about 1300° C. in an atmosphere selected from the groupconsisting of oxygen, nitrogen and air to produce a ceramic of(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.35.
 2. A process for preparing(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.35 comprising, mixing(PbCO₃)₂Pb(OH)₂ of a particle size less than about 4 μm, MgNb₂O₆ havinga specific surface area of more than about 7.5 m²/g and fumed TiO₂having a specific surface area of more than about 50 m²/g to form amixture, the (PbCO₃)₂Pb(OH)₂, the fumed TiO₂, and the MgNb₂O₆ present inamounts sufficient to produce a ratio of (PbCO3)₂Pb(OH)₂:MgNb₂O₆:fumedTiO₂ of about 1:0.256:0.109. milling said mixture in distilled water toproduce a slurry having particle size of less than about 1 μm, heattreating the slurry to produce a dried precursor powder, grinding thedried precursor powder to produce a ground dried precursor powder ofless than about 90 μm, and sintering the dried precursor powder to about1000° C. to about 1150° C. in oxygen to produce a ceramic product of(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.35.
 3. A process for preparing(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.35 comprising, mixing(PbCO₃)₂Pb(OH)₂ of a particle size less than about 4 μm, MgNb₂O₆ havinga specific surface area of more than about 7.5 m²/g and fumed TiO₂having a specific surface area of more than about 50 m²/g to form amixture, the (PbCO₃)₂Pb(OH)₂, the fumed TiO₂, and the MgNb_(2O) ₆present in amounts sufficient to produce a ratio of(PbCO₃)₂Pb(OH)₂:MgNb_(2O) ₆:fumed TiO₂ of about 1:0.256:0.109. millingsaid mixture in distilled water to produce a slurry having particle sizeof less than about 1 μm, heat treating the slurry to produce a driedprecursor powder, grinding the dried precursor powder to produce aground dried precursor powder of less than about 90 μm, and sinteringthe dried precursor powder to about 1000° C. to about 1150° C. in oxygenand then in nitrogen to produce a ceramic product of(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.35.
 4. A process for preparing(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.35 comprising, mixing(PbCO₃)₂Pb(OH)₂ of a particle size less than about 6 μm, MgNb₂O₆ havinga specific surface area of more than about 5 m²/g and fumed TiO₂ havinga specific surface area of more than about 30 m²/g to form a mixture,the (PbCO₃)₂Pb(OH)₂, the fumed TiO₂, and the MgNb₂O₆ present in amountssufficient to produce a ratio of (PbCO₃)₂Pb(OH)₂:MgNb₂O₆:fumed TiO₂ ofabout 1:0.24:0.1 to about 1:0.0.27:0.12, milling the mixture indistilled water to produce a slurry having particle size of less thanabout 3 μm, heat treating the slurry to produce a dried precursorpowder, grinding the dried precursor powder to produce a ground driedprecursor powder of a size less than about 200 μm, compressing theground dried precursor powder to produce a green preform, placing thegreen preform in an embedding powder which can generate lead oxideduring sintering of the green preform, and sintering the green preformto a temperature of about 900° C. to about 1300 ° C. in an atmosphereselected from the group consisting of oxygen, nitrogen and air toproduce a ceramic of (1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.35. 5.The process of claim 4 wherein the sintering of the green preform is ata temperature of about 1000° C. to about 1150° C.
 6. The process ofclaim 5 wherein the sintering is in oxygen.
 7. The process of claim 6wherein the sintering is first in oxygen and then in nitrogen.
 8. Aprocess of manufacture of a single crystal of 0.65PMN-0.35PT comprising,mixing (PbCO₃)₂Pb(OH)₂ of a particle size less than about 6 μm, MgNb₂O₆having a specific surface area of more than about 5 m²/g and fumed TiO₂having a specific surface area of more than about 30 m²/g to form amixture, the (PbCO₃)₂Pb(OH)₂, the fumed TiO₂, and the MgNb₂O₆ present inamounts sufficient to produce a ratio of (PbCO₃)₂Pb(OH)₂:MgNb₂O₆:fumedTiO₂ of about 1:0.24:0.1 to about 1:0.0.27:0.12, milling said mixture indistilled water to produce a slurry having particle size of less thanabout 3 μm, heat treating the slurry to produce a dried precursorpowder, grinding the dried precursor powder to produce a ground driedprecursor powder of a size less than about 200 μm, compressing the driedground powder to produce a compressed preform, placing a barium titanatesingle crystal on the compressed preform, depositing an additionalamount of the ground dried precursor powder over the barium titanatesingle crystal, compressing the preform having the dried precursorpowder and barium titanate single crystal thereon to produce a compact,and sintering the compact to produce a single crystal of 0.65PMN-0.35PT.9. The method of claim 8 wherein sintering is performed at 1150° C. in99% pure oxygen for one hour followed by sintering at 1150° C. innitrogen for ten hours.
 10. A process for preparing a lead magnesiumniobate-lead titanate product comprising, mixing a blend including alead-containing substance selected from the group consisting of leadacetates-lead hydroxides, lead acetates, lead hydroxides and leadcarbonates with magnesium niobate and fumed titanium oxide to form amixture, milling the mixture to produce a blend having particle size ofless than about 3 μm, heat treating the blend to produce a driedprecursor powder, and sintering the dried precursor powder to atemperature of about 900° C. to about 1300° C. to produce a leadmagnesium niobate-lead titanate compound.
 11. The process of claim 10wherein the milling of the mixture is performed by ball milling indistilled water.
 12. The process of claim 11 wherein the leadacetate-hydroxide is Pb(CH₃COO)₂Pb(OH)₂.
 13. The process of claim 11wherein the lead acetate is Pb(CH₃COO)₄.
 14. The process of claim 11wherein the lead carbonate-hydroxide is (PbCO₃)₂Pb(OH)₂.
 15. The processaccording to claim 14 wherein the (PbCO₃)₂Pb(OH)₂ has a particle sizeless than about 6 μm.
 16. The process according to claim 14 wherein themagnesium niobate has a specific surface area of more than about 5 m²/g.17. The process according to claim 14 wherein the fumed titania has aspecific surface area of more than about 30 m²/g.
 18. The process ofclaim 8 wherein the lead magnesium niobate-lead titanate compound hasthe formula (1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x is about 0.0 toabout 0.95.
 19. The process of claim 17 wherein the lead magnesiumniobate-lead titanate compound has the formula(1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x is about 0.0 to about 0.40. 20.The process of claim 17 wherein the lead magnesium niobate-lead titanatecompound has the formula (1−x)Pb(Mg_(⅓)Nb_(⅔))O₃−xPbTiO₃ where x=0.35.21. The process according to claim 10 wherein the blend furthercomprises an oxide of a metal selected from the group consisting of Zr,Ta, La, Fe, Mn, Ni, Zn, and W and mixtures thereof.
 22. The processaccording to claim 10, wherein the blend further comprises a binder. 23.The process according to claim 22, wherein the binder is selected fromthe group consisting of polyvinyl alcohol, polyethylene glycol,methylcellulose, carboxymethylcellulose, ethylcellulose,hydroxpropylcellulose, polyethylene oxide base high polymers, acrylicbase high polymers, maleic anhydride base high polymers, starch,gelatine, polyoxyethylene alkyl ether, polyvinyl butyrol and waxes. 24.A process of manufacture of textured 0.675PMN-0.325PT ceramiccomprising, mixing (PbCO₃)₂Pb(OH)₂ of a particle size less than about 4μm, MgNb₂O₆ having a specific surface area of more than about 7.5 m²/gand fumed TiO₂ having a specific surface area of more than about 50 m²/gto form a blend, milling the blend in water to produce a mixture, dryingthe mixture to produce a dried precursor powder, grinding the driedprecursor powder to produce a ground precursor powder of a size lessthan about 90 μm, mixing the ground precursor powder with an organicliquid, an organic binder and SrTiO₃ single crystal templates to form aslurry, milling the slurry to a particle size of about 1 μm to form amilled slurry, tape casting the milled slurry to form a tape, cuttingthe tape into a plurality of shapes, stacking the shapes into anassembly, compressing the assembly to form a laminated sample, heatingthe laminated sample to burn out the binder to produce a green preform,and sintering the preform to form textured 0.675PMN-30 0.325PT.
 25. Themethod of claim 24 wherein sintering is performed at 1150° C. in 99%pure oxygen for 10 hours to 50 hours.
 26. The method of claim 24 whereinsintering is performed at 1150° C. in 99% pure oxygen for 10 hours. 27.The method of claim 26 wherein the heating of the sample is performed byfirst heating the sample at 0.5° C./min to 200° C., holding at 200° C.for 1 h, heating at 0.35° C./min to 275° C., holding at 275° C. for 1 h,heating at 0.5° C./min to 600° C., holding at 600° C. for 1 h, and thencooling to room temperature at 2° C./min in air.
 28. The product of theprocess of claim
 26. 29. The method of claim 27 wherein the size of theSrTiO₃ single crystal templates is about 1 μm to about 50 μm in edgelength, and about 1 μm to about 10 μm in thickness.
 30. The method ofclaim 27 wherein the size of the SrTiO₃ single crystal templates isabout 5 μm to about 25 μm in edge length, and about 1 μm to about 10 μmin thickness.
 31. The method of claim 27 wherein the size of the SrTi0₃single crystal templates is about 5 μm to about 25 μm in edge length,about 2 μm to about 5 μm thickness.
 32. The method of claim 27 whereinthe ground precursor powder is calcined prior to mixing with the organicliquid.
 33. The method of claim 24 wherein the sintering is performed inair.
 34. A process of manufacture of a single crystal of 0.65PMN-0.35PTcomprising, mixing (PbCO₃)₂Pb(OH)₂ of a particle size less than about 6μm, MgNb₂O₆ having a specific surface area of more than about 5 m²/g andfumed TiO₂ having a specific surface area of more than about 30 m²/g toform a mixture, the (PbCO₃)₂Pb(OH)₂, the fumed TiO₂, and the MgNb₂O₆present in amounts sufficient to produce a ratio of(PbCO₃)₂Pb(OH)₂:MgNb₂O₆:fumed TiO₂ of about 1:0.24:0.1 to about1:0.0.27:0.12, milling said mixture in distilled water to produce aslurry having particle size of less than about 3 μm, heat treating theslurry to produce a dried precursor powder, grinding the dried precursorpowder to produce a ground dried precursor powder of a size less thanabout 200 μm, compressing the dried ground powder to produce acompressed preform, placing a lead titanate single crystal on thecompressed preform, depositing an additional amount of the ground driedprecursor powder over the lead titanate single crystal, compressing thepreform having the dried precursor powder and barium titanate singlecrystal thereon to produce a compact, and sintering the compact toproduce a single crystal of 0.65PMN-0.35PT.